It is well known that loaded railroad cars (railcars) are typically weighed to determine the weight of the carried load. To this end, a number of known techniques have been developed to weigh loaded railcars.
One known technique for weighing loaded railcars is represented in FIG. 1. According to this technique, a railcar 5 to be weighed is uncoupled from the other railcars of a train and rolled over a scale platform 10 that is longer than the railcar being weighed. This weighing technique may be performed both by stopping the railcar 5 on the scale platform 10 until a stable weight is captured, or by rolling the railcar down a grade and capturing the weight of the railcar while the entire railcar resides on the scale platform. This technique is commonly referred to as a single draft weighing technique. The single draft weighing technique has proven to be the most accurate method of weighing railcars. However, as should be apparent, it is also very inefficient.
A first coupled-in motion (CIM) technique for weighing loaded railcars is represented in FIG. 2. This technique is commonly referred to as wagon weighing. According to this technique, a loaded railcar 15 can be weighed while moving and while still coupled to the other railcars of a train. Weighing is accomplished by using two or three scale platforms of different lengths that, when combined, are longer than the longest railcar to be weighed. In the example shown in FIG. 2, two scale platforms 20, 25 are present. Track sensors 30 and software logic are used to determine when both wheel carriages 35, 40 of a given railcar are respectively isolated on the two platforms 20, 25, and a weight is captured. This improves the efficiency of the weighing process by eliminating the need to un-couple, weigh and then re-couple the railcar to the train—as must be done in accordance with the single draft weighing technique. One disadvantage of this method is that the number of different railcars that can be weighed is limited by the distance between railcars (i.e., the wheel carriages of two different railcars may simultaneously reside on the longer scale platform if the distance is too short). When the railcar-to-railcar distance falls outside of an allowed distance, the associated operating software reverts to a dual draft weighing method (see below).
Another known CIM technique for weighing loaded railcars is represented in FIG. 3. This technique is commonly referred to as a dual draft weighing method. According to this technique, a railcar 45 is weighed by taking a weight reading during the dissimilar points in time when an individual first and then second wheel carriage 55, 50 of the moving railcar separately resides on a single scale having a short scale platform 60 that is only slightly longer than a wheel carriage of the railcar. The weight measurements captured by the scale with respect to each wheel carriage of the railcar are subsequently added together to determine the total railcar weight. This short platform CIM weighing method is generally the most cost effective method for weighing railcars.
The CIM dual draft weighing method works well for railcars with stable loads. However, when the commodity being moved by the railcar is flowable (e.g., a liquid), the load typically shifts (i.e., oscillates) while the railcar is moving on the rails. This oscillation degrades the dual draft weighing process since the spacing between the railcar wheel carriages is frequently sufficient lengthy so as to permit the occurrence of a weight shift from one wheel carriage toward the other within the time between weighing the first and second wheel carriages.
Therefore, there is a need for more accurately weighing a moving railcar carrying flowable or otherwise other non-stationary (i.e., displaceable) load. Systems and methods of the present invention allow for such weighing operations.